Reply to Oreska et al 'Comment on Geoengineering with seagrasses: is credit due where credit is given?'

In their comment on the review paper, 'Geoengineering with seagrasses: is credit due where credit is given?,' Oreska et al 2018 state that some of the concerns raised in the review 'warrant serious consideration by the seagrass research community,' but they argue that these conce...

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Bibliographic Details
Published in:Environmental research letters 2018-03, Vol.13 (3), p.38002
Main Authors: Johannessen, Sophia C, Macdonald, Robie W
Format: Article
Language:English
Subjects:
blue carbon
Carbon
carbon burial
carbon credits
Carbon offsets
Carbon sequestration
Emissions control
Emissions trading
Geoengineering
Lead isotopes
Remineralization
seagrass meadows
Seagrasses
sediment cores
Sediments
Surface layers
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Summary:In their comment on the review paper, 'Geoengineering with seagrasses: is credit due where credit is given?,' Oreska et al 2018 state that some of the concerns raised in the review 'warrant serious consideration by the seagrass research community,' but they argue that these concerns are either not relevant to the Voluntary Carbon Standard protocol, VM0033, or are already addressed by specific provisions in the protocol. The VM0033 protocol is a strong and detailed document that includes much of merit, but the methodology for determining carbon sequestration in sediment is flawed, both in the carbon stock change method and in the carbon burial method. The main problem with the carbon stock change method is that the labile carbon in the surface layer of sediments is vulnerable to remineralization and resuspension; it is not sequestered on the 100 year timescale required for carbon credits. The problem with the carbon burial method is chiefly in its application. The protocol does not explain how to apply 210Pb-dating to a core, leaving project proponents to apply the inappropriate methods frequently reported in the blue carbon literature, which result in overestimated sediment accumulation rates. Finally, the default emission factors permitted by the protocol are based on literature values that are themselves too high. All of these problems can be addressed, which should result in clearer, more rigorous guidelines for awarding carbon credits for the protection or restoration of seagrass meadows.
ISSN:1748-9326
1748-9326
DOI:10.1088/1748-9326/aaae71